Splitting a single zone system question.

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  #1  
Old 06-03-19, 02:46 PM
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Splitting a single zone system question.

My sons home has a single zone HWBB system with a common return (1 1/4) Not 3/4 as shown on in the picture.

The house is a ranch, open basement the two legs merge into the return at the center of the house at the furthest end. (see picture)

Question:
Can I just install zone valve on each leg and still use the common return as piped?
Or do I need to bring a separate return back for each branch.

 
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  #2  
Old 06-03-19, 04:43 PM
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ny,
If that drawing is typical of your system then you can just add a zone valve to split the system and come back into the common return.
 
  #3  
Old 06-04-19, 06:34 AM
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Yes this is exactly what he has right now.

Thanks that will save some money and time!

I assume I might need a mono flow just before the merge to the return to prevent flow back into the other zone or will the zone valve keep that from happening. This of course is the case of one zone operating and the other is off
 
  #4  
Old 06-04-19, 07:31 AM
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prevent flow back into the other zone
The zone valve will prevent back flow. The pipe in the inactive zone adjacent to the merge may get slightly warm due to conduction but not enough to worry about.
 
  #5  
Old 06-04-19, 02:18 PM
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Thanks!

That helps a lot.. I have a plan now.

Thanks to all for the help!
 
  #6  
Old 06-04-19, 03:50 PM
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All you will need is a 24V 40va transformer, 2 zone valves and a t-stat and you're on your way.
 
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Old 06-05-19, 06:25 AM
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All you will need...
May also need a zone control panel or relay to manage the pump. Otherwise how to keep pump from running against 2 closed valves when no heat call from either zone.
 
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Old 06-05-19, 07:35 AM
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MJH can use thermostats to open zone valves and their end switches to activate circulator.

I have 8 zones where valve switches activate circulator relay. You do not need zone controller.

Had 1 zone, split level house similar to my_jets_head diagram. Hot water from boiler went to upper center point of system and returns through elements closest to boiler. Opposite to NJH system.

First split into upper and lower level zones. Later added zones for basement and mid level area.

Another option for one circulator system is to use auto sensing Grundfos -Alpha circulator left powered on at all times. It will automatically adjust flow.

https://www.supplyhouse.com/Grundfos...w-Terminal-Box
 
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Last edited by doughess; 06-05-19 at 08:04 AM.
  #9  
Old 06-05-19, 10:44 AM
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You do not need a ZC panel. Your pump will only come on when either stat calls if wired properly with the stock I've listed. The end switches from your ZV's will go to TT on the boiler just as your stat does now.

2J,
It is just a series circuit. From the xformer - stat, from stat- #1 on ZV. #2 on ZV back to xformer. That will open ZV on a call for heat from stat. and make an end switch #2 & #3 on TACO ZV. if that brand is used and that will go back to TT on aquastat on boiler operating burner and pump circuit until stat is satisfied. Other ZV brands may have 4 wires so #3 &4 would go to TT but same principle applies.

If TACO is used you can put up to 3 ZV's on a 40VA transformer. Not all stats support TACO ZV's because of their high amperage draw. You must get one that goes to .9 amps or ZV could act erratically and will have a shorter life span.
 
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Last edited by spott; 06-05-19 at 11:01 AM.
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Old 06-05-19, 07:49 PM
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Spott: The end switches from your ZV's will go to TT on the boiler just as your stat does now.
Spott is wrong. Zone valve end switches should activate circulator not burner. Except for cold start, hydronic system burners are controlled by boiler aquastat, not room thermostats.

Some zone control panels also have aquastat function which can confuse issue. The zone and burner activation are independent, parallel issues and not linked.

Regarding back flow. In most systems, closed zone valves prevent back flow. When open they are parallel loop.

2john02458 Otherwise how to keep pump from running against 2 closed valves when no heat call from either zone.
The Grundfos-Alpha circulator kept powered on "idles" when zone valves are closed.
It senses when one or more ZV's open and adjust flow accordingly. Welcome to the modern world!

The Grundfos-Alpha uses 50% less electricty and cost 50% less than widely used red Bell & Gosset Series 100 circulator. https://www.supplyhouse.com/Bell-Gos...Pump-3540000-p

This is another classic heating system situation where new technology products are far better and cost less than old technology products.

In the high technology world they are called "legacy products." People keep buying the old for premium prices. Duh, duh, duh.
 
  #11  
Old 06-05-19, 08:15 PM
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Doug.........................

Spott: The end switches from your ZV's will go to TT on the boiler just as your stat does now.
Spott is wrong. Zone valve end switches should activate circulator not burner. Except for cold start, hydronic system burners are controlled by boiler aquastat, not room thermostats.
Aren't the TT terminals on the aquastat ?
Doesn't the aquastat control the circulator and the burner ?
Doesn't shorting the TT terminals start the circulator and then the boiler if more temp is needed ?
 
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Old 06-06-19, 03:33 AM
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WOW, a pi**ing contest between 2 long time members Doughess and Spott. I thought that we were not supposed to judge any other members for their answers that we deem wrong. I know this because I have been told about it a couple times. Every time I tried to correct someone I would get smacked down. That is why I have reservations about this site; wrong answers are allowed. (my 2 cents). That said, you both could be right, depending on the age of the system, the type of boiler and how it is controlled and wired. However, I think that Spotts answer is closer to the correct one. A more detailed explanation of the boiler and it's controls are needed to know the exact correct answer.
 
  #13  
Old 06-06-19, 06:50 AM
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This was not a judgment call but a matter of fact. Connecting the boiler TT terminals activates the boiler.
Spott was specific: The end switches from your ZV's will go to TT on the boiler.
Yes, other units on heating system can have TT terminals. Sometimes they are wired in series. The TT terminals on my burner, aquastat, electric stack switch open and boiler over temperature unit are in series. Note that thermostats, zone valves, end switch and zone panels are not in that control loop.

Safety is key in heating systems. All necessary conditions should be met to enable firing burner.

Thinking in terms of unit function, rather than terminal name makes it easier to understand system operation.

With abstract terminal names, is easy to get lost in what is happening when thinking of connecting terminals W to X to Y to Z . Service people do not have to know thermodynamics, just where to connect things.
 

Last edited by doughess; 06-06-19 at 07:35 AM.
  #14  
Old 06-06-19, 12:03 PM
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I was debating weather to respond to doughess' comments or just let it go and consider the source as I have done so many times in the past. This will be my one and only response.

As Pete mentioned and obviously understood what was meant, the TT terminals are on the aquastat and if doughess would have read the complete #9 post he would have seen that also. It was a general statement that only meant the stat wires end up back at the boiler and obviously the aquastat where his current wires are at right now. It was only a statement that meant his wires would end up at the same place.

Where the OP already had a working system and was going to do the work himself and my post was for him I assumed he has some idea of how the system works or he would have asked.

As far as series circuits go I do not know of any heating system weather it be steam or hot water or warm air that is not series circuit wired. If any component fails within that circuit the unit will not fire for safety reasons.

Steamboy, you are correct in your statement also. The age of the system and what it's being used for does make a difference in the way it's wired but in this case I just answered a specific question and your statement would only come from someone who obviously has been in the business with field experience and not childishly nitpicking at every word.

Pete, your explanation is exactly right. At or On boiler I assumed the OP knew it was the TT on the aquastat that was the final destination for the wiring.
 

Last edited by spott; 06-06-19 at 12:18 PM.
  #15  
Old 06-09-19, 12:33 PM
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Pjmax #11: Aren't the TT terminals on the aquastat ?
Doesn't the aquastat control the circulator and the burner ?
Doesn't shorting the TT terminals start the circulator and then the boiler if more temp is needed
First define aquastat: a device used in hydronic heating systems for controlling water temperature. In simplest terms a temperature activated switch with two contacts typically unlabeled.

Next define TT terminals: On HVAC equipment option for low voltage/ 24 VAC control TT terminals when connected together enable a item operation when other conditions for the item are met.

Part of the confusion comes from items called aquastats that are multi functional. Both Honeywell and Taco make aquastats. Some have only 2 terminals to start/activate a burner, circulator or whatever with either 24VAC or 120VAC. Their other aquastats have multiple terminals including a TT pair and may function as oil burner primary control, circulator relay or boiler aquastat.

Those multi functional units only have one pair of TT terminals. At installation how those units are wired and setup determines what TT activates. See page 3:
https://s3.amazonaws.com/s3.supplyho..._PROD_FILE.pdf
 
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